Forced water cooling of thick steel wires

Abstract

A method of and an equipment for controlled cooling of one or multiple previously heated, straight, and thick steel wire to a predetermined temperature range between 400.degree. C. and 650.degree. C. Each of the thick steel wires is subjected to a controlled cooling-transformation treatment from austenite to pearlite, which occurs substantially after the wire leaves a forced water cooling length.

Description

TECHNICAL FIELD[0001]The present invention relates to a method and an equipment for controlled cooling of steel wires.BACKGROUND ART[0002]Heat treatment of steel wires usually plays an important role in the art of wire-making. The first step in wire-making starts with drawing a wire rod to a desired intermediate diameter which can vary from 1.0 to 5.0 mm or more. At this stage of work-hardening the drawn wires are heat treated to pearlite by a patenting process to enable further plastic deformation. Subsequently, the patented steel wires are drawn to a smaller size, either a second intermediate size or a final diameter. Patenting involves heating carbon steel wires into the austenitic phase, generally above 800° C. and then cooling the wires to a chosen temperature held for a sufficient period for generally isothermal decomposition of the austenite to be completed. The temperature is usually in the region of 550° C., with the intention being generally to provide a fine pearlite stru...

AI Technical Summary

Benefits of technology

The invention is a way to cool down previously heated steel wires using a liquid coolant and a steam film. By directing the coolant towards the steam film, the thickness of the film can be reduced or made unstable, which speeds up the cooling process. The equipment is cheap and easy to adapt, and can cool wires of different diameters by adjusting the immersion length and cooling length individually.

Problems solved by technology

However, this method has been regarded as being less suitable or unreliable for treatment of wires with other diameters.

Austenite to pearlite transformation may also be done in a water bath, however, if there is only one water bath provided, it may give problems for wire diameters smaller than 2.8 mm and even becomes impossible for wire diameters smaller than about 1.8 mm as the cooling velocity / speed of such a steel wire is too fast, which further causes unfavourable metallic structure of the patented steel wire.

Up to now prior attempts to use the aforementioned methods for the purpose of effecting a cooling-transformation of drawn and austenitized thick steel wires to pearlite, have been largely unsuccessful in many respects.

The results of the heat treatment are too often unreliable and the treated thick wires show too high a variation in properties such as inconsistent drawability and frequently unexpected brittle behaviour because of numerous undesirable metallic structures.

On the other hand, the metallic structure of the patented steel wire must not be too soft, i.e. it must not present too coarse a pearlite structure or too great a quantity of ferrite, since such a metallic structure would never yield the desired ultimate tensile strength of the steel wire.

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